1. Field of the Invention
The present invention relates to heat exchangers of the tube and shell type wherein a first fluid passes within a plurality of hollow, heat transfer tubes while a second fluid passes in indirect heat exchange with the first fluid through the spacing between the transfer tubes and the surrounding shell of the exchanger. In such exchangers, there has long been a problem of maldistribution of the fluid flow through the shell side of the exchanger. More specifically, there is a distinct tendency of the fluid introduced at the inlet of the shell side to flow in the shortest, most direct path to the outlet region of the exchanger instead of flowing uniformly in counter current heat exchange with the fluid flowing within the heat transfer tubes. While this maldistribution problem may exist in exchangers of various sizes and relative dimensions, it is particularly acute in heat exchangers in which the inlet and outlet are longitudinally spaced in the same direction in which the transfer tubes extend, and can be particularly severe in exchangers having relatively large diameters and relatively short longitudinal lengths.
2. Prior Art
U.S. Pat. No. 4,593,757 assigned to the Phillips Petroleum Company represents one prior art attempt to minimize the above-indicated maldistribution problem by varying the number and position of the support rods in a rodbaffle heat exchanger such that fewer rods are positioned adjacent the inlet and outlet regions of the exchanger than at other portions so that the flow of the shell side fluid is forced to flow in a more uniform and desirable direction.
Another attempt to solve the above-indicated maldistribution problem is disclosed in U.S. Pat. No. 4,289,198 assigned to the Phillips Petroleum Company. This patent discloses the use of rod baffle means in the form of a set of flow deflecting or directing rods positioned in the spaces between adjacent rows of tubes in order to provide improved shell side fluid distribution.
A further attempt to improve the overall distribution of the beat exchange fluid in the shell side of the exchanger is disclosed in U.S. Pat. No. 4,588,024 assigned to the Phillips Petroleum Company. This patent discloses the use of rectangular plates between pluralities of helical tubes so as to block the flow of the shell side fluid in some regions and force the flow through other regions of the shell side passage ways.
Each of the above-indicated disclosures has been successful in improving the shell side flow distribution; however, each has had its own disadvantages such as, for example, time-consuming and difficult manufacturing steps, and/or undesirably high cost of the exchanger.
The present invention solves the maldistribution problem on the shell side of a tube and a shell exchanger by the simple provision of a plurality of disks surrounding selected heat transfer tubes. The discs are in the path of shortest distance between the inlet and outlet of the exchanger, and are concentrated in the inlet and outlet regions so as to force more flow into a more uniformly distributed and more effective beat transfer pattern. The disks of the present invention are relatively inexpensive and are easy to install on the tubes during the assembly of the exchanger. As a result, they substantially improve the flow distribution at lower cost and with easier manufacturing steps than has been previously possible.